the period during which the oocyte matures in the ovary, is ovulated, and enters the uterus through the uterine tube; ovarian hormonal secretions affect endometrial changes. The endometrial menstrual cycle has four phases: proliferative, luteal, ischemic, and menstrual. The cycle lasts an average of 28 days with day 1 of the cycle designated as that day on which menstruation (menstrual flow) begins. Cf.: menstrual cycle